Paper Sensors Based on Fluorescence Changes of Carbon Nanodots for Optical Detection of Nanomaterials

Abstract

A paper sensor was designed in order to detect the presence of nanomaterials, such as ZnO and silica nanoparticles, as well as graphene nanoplatelets (GnP), based on fluorescence changes of carbon nanodots. Paper strips were functionalized with carbon nanodots using polyvinyl alcohol (PVA) as binder. The carbon nanodots were highly fluorescent and, hence, rendered the (cellulosic) paper stripes emissive. In the presence of silica and ZnO nanoparticles, the fluorescence emission of the carbon nanodots was quenched and the emission decay was shortened, whereas in the presence of GnP only emission quenching occurred. These different photoluminescence (PL) quenching mechanisms, which are evident from lifetime measurements, convey selectivity to the sensor. The change in fluorescence of the carbon dot-functionalized paper is also evident to the naked eye under illumination with a UV lamp, which enables easy detection of the nanomaterials. The sensor was able to detect the nanomaterials upon direct contact, either by dipping it in their aqueous dispersions, or by sweeping it over their powders. The use of the proposed optical sensor permits the detection of nanomaterials in a straightforward manner, opening new ways for the development of optical sensors for practical applications.

Tunable and white light photoluminescence from ZnO on porous Si with the addition of carbon quantum dots

“…The addition of the dots did not significantly affect the emission color of the ZnO part. It has been previously demonstrated that the presence of ZnO quenches the emission of the carbon quantum dots due to electron-hole recombination caused by non-radiative electron transfer between the materials [39][40][41]. On the other hand it turned the porous Si part from red to purple, as expected.…”

Prevention-through-design approach to mitigate workers’ exposure in the graphene production processes

“…buccal micronucleus by cytome assay on exfoliated buccal cells, direct/oxidative DNA damage by blood-Fpg comet assay on venous blood samples and 8-oxodGuo urinary oxidized bases by urine samples [36]. -Use of point-of-care sensors as described by Papadoupolou et al 2021 [38] (Patent no.…”

Antifibrotic activity of carbon quantum dots in a human in vitro model of non-alcoholic steatohepatitis using hepatic stellate cells

“…The photoluminescence (PL) point for the CDs was found at 472 nm, caused by the sp 2 conjugation of the nucleus that generates a high carbonization and the reduction of functional groups with oxygen on the surface of the CDs, results coinciding with articles previously published by Papadopoulou and collaborators. 38 CD synthesized from citric acid give the CD conjugated carboxyl groups to its surface. When the CDs are conjugated with LF, the intensity of the PL decreases because of the energy transfer required for the protein to conjugate on the surface to the carboxyl groups and form an amide bond, a case that can be easily observed in Fig.…”